1. Field of the Invention
The present invention relates to the field of butt press welding and can be used in different branches of industry and construction for the welding of tubular parts of different configurations and for different purposes.
2. Description of the Prior Art
A machine is known for butt welding (see Author's certificate No. 740436, B.I. No. 22 of 15.06.1980), composed of movable and stationary casings, guides connecting them, upset cylinders for moving the movable casing, supports and a frame. The casings have aligning clamping mechanisms whose designs are similar. In each staple-like casing there is a staple-like semi-ring, which is rotated about the machine axis by means of hydraulic cylinders. Inside, the semi-ring has radial grooves, the center of which is located at a similar distance from the machine axis providing forces during the ring turning which act on an insert of shoes preserving the angle of force action to the insert within 10°-12°, advancing the shoes along radial slots toward the machine axis, whereby clamping and aligning of a workpiece is performed. The ring, during the reverse movement, is acting by grooves which are located on the external surface, to special rests of shoes, removing the shoes to an initial position.
There are the following drawbacks in the design of this prior machine:                1. the alignment device is designed for aligning rods and distortion and deterioration of alignment are possible when aligning pipes;        2. the staple-like casing has a low rigidity, thus leading to an increase in its weight and also deterioration of the alignment components;        3. there are large losses in the clamping drive due to the fact that the cramp-like ring is simultaneously under high friction at its external surface on the casing and at its internal surface on the shoe inserts under full force clamping, and        4. it has a complicated mechanism to return the shoes to their initial positions.        
For the same reasons, there are drawbacks to the mechanism of alignment according to the Author's certificate No. 251719, B.I. No. 25 of 07.07.1984 which consists of opening casings, described also in the Author's certificate No. 740436, i.e. insufficient rigidity, large mass, high frictional losses, as the semi-rings in movement under clamping load are subjected to friction on the internal surface of the casings and on the shoe slopes by their inserts.
In the design according to the Author's certificate No. 361050, B.I. No. 1 of 1972, there are the same drawbacks that were described in earlier mechanisms of alignment, the only advantage being a large rigidity of the device, as a non-detachable circular casing is available.
A clamping aligning device for a butt welding machine is taken as a prototype according to the Author's certificate No. 231041, B.I. No. 35 of 15.11.1968, which consists of moveable and stationary casings, swinging cylinders of a ring drive which is located in the middle of the casings and aligned along the internal surfaces of the casings. Into the ring, cylindrical inserts are pressed-in, whose lateral surface projects beyond the ring internal surface and contacts during ring rotation the variable-angle slopes of clamping shoes, advancing them along radial guides in the casing to the pipes. A slope with a large angle is designed for a fast shoe feed toward the pipes, while the force necessary for generation of a clamping force is developed at a slope with a smaller angle. The shoes have a possibility of radial movement in radial slots in the casings.
In addition, in the column casings are mounted variable-arm levers which are rotated around pins fixed in the casings. One lever arm interacts with special projections of the ring, and a second arm enters the shoe slot and returns the shoe to an initial position when the ring is rotated in reverse.
Movable and stationary casings are interconnected by four guides. Moreover, at the ends of the guides, which pass through the movable casing, the pistons of a flashing and upsetting mechanism are mounted, whose cylinders are fixed on the movable casing.
As all the clamping force is imparted to the ring, then, under its action, ring deformation and an increase in its frictional force on the casing are possible. This is a considerable disadvantage of that prior design because the required drive force is increased.
Another drawback is that the machine requires a complicated mechanism for shoe return to their initial positions, and the return itself is not precise. This leads to an increase in the dimensions of casings and rings, thus increasing greatly the mass of casings.
Another large drawback is the required transition through a crest between shoe slopes with different angles. This leads to jumpy movement of the shoes and increased wear both of the ring inserts and the shoe slopes.
Besides, the repair and maintenance of the machine are complicated. For example, the replacement of a collar in a flashing and upsetting cylinder requires that the machine be dismantled.